DESCRIPTION: Non-medical prescription opioid (NMPO) use is a serious public health problem in the United States. Although NMPO-related health and social harms, including opioid dependence, lost productivity, and overdose are major causes of morbidity and mortality, initiation of injection drug use and infectious disease specific consequences, including HIV and hepatitis C virus (HCV) infection, are crucially understudied. The objective of this project is to examine the context and epidemiology of injection drug use as well as HIV- and HCV-related risk behaviors among young adult NMPO users. The ultimate goal of this pilot study is to use these data to inform the development of a prospective cohort study to determine the multi-level risk factors for initiation of injection drug use in this population. Specifically, the proposed stdy has the following aims: (1) to compare and evaluate the feasibility of two novel sampling methods to recruit young adult NMPO users; and (2), to explore social, macro-social, and drug-related factors associated with HIV risk behavior and transitions to injection drug use among young adult NMPO users. To achieve these aims, we will conduct a pilot study of 200 NMPO users aged 18 to 25 who reside in Rhode Island (RI), a state that is among the highest in the prevalence of NMPO use among young adults. To achieve Aim 1, we will compare the efficiency, cost, and sample composition of two novel recruitment strategies, including a combination of targeted canvassing and respondent-driven sampling, as well as mixed internet-based recruitment from drug information and social media websites. To achieve Aim 2, we will assess non-injectors' perceptions of risk for initiating injection. We will also examine the relationship between social, macro-social, and drug-related risk factors (e.g., diversion from family members, social network characteristics, denial of opioids for pain control, progression to heroin use following abuse-deterrent reformulations) and HIV risk behaviors and transitions to injection drug use. Finally, to assess receipt of opioid prescriptions from multiple physicians as risk factor for injecting initiation, we will obtain past-year opioid dispensation histories by conducting a deterministic, confidential data linkage to the RI prescription monitoring program. This study has important implications for improved prescription opioid exposure assessments as well as the development of novel sampling methodologies to access members of a population that, due to the hidden and amorphous nature of NMPO use, has been challenging to study. This research will address several questions central to the urgent public health challenges facing non-medical users of prescription opioids in the US, particularly in the context of evolving technologies and abuse-deterrent formulations to prevent injecting and opioid abuse. Taken together, the results of this work will inform the development of interventions to prevent injectin initiation and reduce HIV transmission in NMPO-using populations, and avert unintended adverse consequences of ongoing prescription opioid prescribing and policy changes.